Stanford University School of Medicine is evaluating the Pathwork Tissue of Origin Test, which measures the expression of more than 1,500 genes to compare a tumor's gene expression profile to those of 15 known tissues and provide a probability-based score for each potential tissue, Pathwork Diagnostics Inc. said.

"Hard-to-identify tumors are particularly challenging for physicians," Dr. Iris Schrijver, director of molecular pathology at Stanford, said in a statement. "Clinical workups for these patients can be time-consuming, expensive and frustrating for both the physician and the patient, particularly when traditional diagnostic approaches are unable to provide answers."

In a cross-laboratory comparison study of 60 metastatic and poorly differentiated and undifferentiated tissue specimens, the test demonstrated an average 94 percent overall concordance across four laboratories. The findings were published in the Journal of Molecular Diagnostics.